However, I'm still seeing it on our 5.06 as well as on Zimbra's demo server, so think maybe it's been re-introduced somehow.

I've sent this into support, but they've still not verified it. I've recreated it from two different machines (Mac & Windows FF).

I've done exactly this to recreate:

1. Open the calendar
2. Double-click on a Monday (say, 9/8) to create a new appointment
3. Fill with a subject (say, test1) and click More Details
4. In the detailed set up window, change the date to a Friday, (e.g. 9/12)
5. Set the appointment to repeat every week
6. Add yourself as an attendee and save.
7. Examine the invitation email, and you should see something like:

Recurrence : Every Monday. No end date. Effective Sep 12, 2008.

Note that it reads every "Monday", while the actual appontments are on Friday.

This bug still shows up in 5.0.11. Our receptionist just picked up on it by doing the following:

Create a new appointment for any day, check it as "All day event" and to repeat every year. Save it and it shows up on the correct day on the calendar. Open up the series and see that next to the Repeat: button will show appointment recurring on *today's* date instead of the appointment date. Change/add any part of the appointment and save, and the subsequent appointments in the series get moved to *today's* date (e.g. every Jan 14th).